The present invention relates generally to ignition systems for internal combustion engines and in particular to improvements in ignition systems of the capacitor discharge type.
In order to reduce the complexity, the number of component parts, the package size, and the cost of capacitor discharge ignition circuits, various circuit arrangements have been tried in an attempt to improve such circuits without sacrificing desired operating performance and reliability. In accordance with such objectives, the prior art includes various circuit arrangements for charging the capacitor during a portion of the engine operating cycle and thereafter discharging the capacitor, through an SCR or the like, at a desired time in the engine cycle.
The present invention is directed to improvments in capacitor discharge ignition systems, and particularly, to a capacitor discharge ignition system having novel features which result in important advantages over prior art capacitor discharge ignition systems. One of these features is the utilization of a single winding for both charging the capacitor and for providing a trigger signal for the SCR whereby the cost and complexity of the system are reduced. Another of these is the provision of an ignition coil on the stator structure having the charge/trigger winding so that the primary winding of the ignition coil is energized, not only by the discharge of the capacitor, but also simultaneously by the magnetic field used to induce a charging current in the charge/trigger winding so as to increase the power supplied to the spark plug. Another feature is a provision in the circuit for resonant charging of the capacitor by which substantially maximum potential on the capacitor is attained at the time at which the capacitor is discharged so as to eliminate the necessity of the usual charging diode for the capacitor. And yet another feature is the connection of the charging coil in series with the discharge path for the capacitor so that the charge winding current augments the current from the discharging capacitor to further improve the potential supplied to the spark plug. Further novel features involve the construction and arrangement of the magnetic circuit structure via which the system is energized and various triggering circuits for the SCR through which the capacitor is discharged into the primary of the ignition coil. By virtue of the several embodiments of the invention disclosed herein, a capacitor discharge ignition system can provide excellent performance over a wide range of engine speeds without the complexity generally associated with prior capacitor discharge ignition systems. Thus, a system according to the present invention may be economically constructed and compactly packaged for use with many types of engines, for example, single cylinder gasoline engines such as are used in power lawn motors, etc. Further advantages and features of the invention will be seen in the ensuing description and claims which are to be taken in conjunction with the accompanying drawing.